Preparation of the indigo-vat employed in dyeing.



HENRI CHAUMAT, OF PARIS, FRANCE.

PREPARATION OF THE INDIGO-VAT EMPLOYED IN DYE Specification of LettersPatent.

Patented April as, 1908.

Application filed August 20, 1907. Serial No. 389,400.

To all whom it may concern:

Be itknown that I, HENRI CHAUMAT, a citizen of the Republic of France,and resident of Paris, France, have invented a new and usefulPreparation of the Indigo-Vat Employed in Dyeing, which improvement isfully set forth in the following specification.

As is known in dyeing the name of "vat is generally given to the bath inwhich the indigo is dissolved. The indigo vat has heretofore beenprepared either by fermentation or by means of chemical products.

The present invention has for its object an electrolytic process wherebyan indigo vat suitable for dyeing may be speedily obtained.

This process consists broadly in treating with an electric current,while protected from the air, a bath of alkaline or alkaline earthsalts, such as :,carbonates, sulfites, bisul 'tes or sulfids, employedeither alone or in the state of mixture and in particular, carbonate ofsoda. The anode at which the current enters the bath is constituted bycarbon or a metal which is not oxidizable under the conditions of theoperation The cathode is formed in the manner hereinafter described,from a special mixture.

In order to form the cathode powdered indigo blue is taken. As in thefermentation processes this powder should be reduced to an impalpablestate. This indigoin powder is mixed intimately with powdered graphiteor a metallic powder which is a conductor of electricity. and by anyappropriate means, such as molding or otherwise, a cathode is producedthe form of which will depend upon the form and dimensions of the vatematmosphere, either a stratum of an insulating liquid such as oil, oran insulating atmosphere, such as carbonic acid. The anode and thecathode described above should be introduced into the bath before thistakes place. The anode may be placed inside a diaphragm.

Under the influence of the electric current oxygen is produced at theanode and this should be disposed of in any convenient manner, forexample by suction in the chamber formed by the diaphragm around theanode; if the bath contains sulfids or sulfites the diaphragm is notnecessary as the oxygen is absorbed by the bath. On the cathode, on theother hand hydrogen is formed this reduces the indigoin and transformsthis insoluble indigoin into indigo white soluble in alkali which isproduced at the cathode in exactly the proper quantity for dissolvingthe indigo white. In proportion as the indigo white is dissolved in thealkaline solution of the bath, which solution is more or less caustic,there forms in the chamber constituted by the diaphragm around thecathode, conducting powder which is disaggregated from this cathode.This conducting powder, is subsequently removed and in any case does notenter the vat which contains the liquid really utilizable for the indigovat. In this manner a solution of indigo white in the more or lesscaustic alkaline salts of the bath is thus obtained very speedily, theproportion being very high. The liquid thus obtained may be prepared onthe spot and be used at once for dyeing; or it may be drawn ofi'rotect'ed from the air and preserved inde nitely in receptacles whichare either soldered or closed in any other hermetic manner.

The importance of this novel process will therefore be understood as itpermits of preparing in advance and in very large quantities the liquidsrequired for theformation of the indigo vat. Again, generally speaking,among the numerous advantages presented by the process forming theobject of the present invention, the following may be cited:1. Thisprocess permits of forming an indigo vat in a few hours while thefermentation processes hitherto employed necessitate a very long timeand constitute excessively delicate operations calling for carefulsurveillance. 2. By this process solutions are obtained which containabsolutely nothing but indigo white and the quantities of more or lesscaustic alkaline salts necessary for dissolving this indigo white. 3.Far more concentrated solutions are obtained than by what are termed thefermentation processes. 4. It is possible to preserve the indigosolution indefinitely in a closed vessel and consequently to place thissolution on the market for use in dyeing. 5. The bath obtained isperfectly homogeneous and its employment in dyeing piece goodsaccordingly gives excellent results as regards the uniformity of theshade obtained. 6. It is very economical. 7. The bath does not containany foreign body and consequently gives a remarkable richness of tone.Having now particularly described and ascertained the nature of my saidinvention and in what manner the same is to be performed, I declare thatwhat I claim is An electrolytic process for the reparation of the indigovat employed in d yeing, consisting in treating by the electric current,with exclusion of air, an alkali solution, lacing an anode in a chamberseparated rom the bath by a diaphragm, said anode being constituted by ametal which is not oxidizable in the conditions of the operation,forming a cathode by a mixture of metallic powder which is a conductorof electricity, and protecting the vat from external oxidation.

In testimony whereof I have signed this specification in the presence oftwo subscribing witnesses.

HENRI OHAU MAT.

